1. Field of the Invention
The present invention relates generally to hand-held measurement devices and, more particularly, to an attachment for the enhanced measurement accuracy of a combination square.
2. Description of the Related Art
As is well known, the combination square performs numerous functions. The graduated numbering on the blade allows the combination square to be used as a normal ruler. When placed on its side, with the blade lying flat against a working surface, such as a table, the combination square is used to square a working surface in the horizontal plane.
When the combination square is placed in the vertical position, with the blade extending out from the handle in the vertical plane, the combination square helps to square an object in the vertical plane.
In order to utilize the ruler portion of the blade and obtain accurate measurements, it is critical that the working surface be squared properly. However, utilizing the combination square to square a working surface is problematic in certain situations.
The first situation problematic for the use of combination squares is squaring an object in the vertical plane. The lower surface of the combination square handle, which horizontally engages and rests upon the working surface being squared, has a small cross sectional area. This small cross sectional area facilitates the rotation of the combination square along the horizontal axis of the handle. This results in inaccurate vertical readings of the object being measured.
Second, this rotational problem is magnified when the working surface being measured has no flat surface in the vertical or horizontal planes to engage the lower surface of the combination square handle. This occurs most often when measuring rounded corners.
Another problem created from the small surface area of the lower surface of the combination square handle involves the use of levels. Several combination squares utilize a bubble level positioned within the handle of the combination square, in a plane parallel to the lower surface of the handle and perpendicular to the edge of the blade. The limited surface area of the lower surface of the handle precipitates rotational distortion of the handle, as discussed above. As a result of this distortion, a stable, accurate, level measurement is made more difficult to obtain.
Examples of devices in the previous art that incorporate plumb levels are U.S. Pat. No. 5,459,935, issued in the name of Paulson et. al., U.S. Pat. No. 5,452,522, issued in the name of Kook et. al., and U.S. Pat. No. 4,503,624, issued in the name of Whiteford.
These devices, however, do not address the rotational problems addressed by the present invention. Furthermore, only the '624 device discloses a combination square. In addition, the '935, '522, and '624 devices disclose squares with additional technology designed to increase measurement accuracy. As such, none of these devices address the need for an attachment that will increase the accuracy of existing, traditional combination squares. Also, the devices do not address the torsional distortion problem discussed above.
Other devices in the previous art disclose various attachments for combination square. These devices, however, are designed to address different needs than that of the present invention. For example, U.S. Pat. No. 5,276,973, issued in the name of Rakauskas, discloses a combination square height/width gage. The device consists of a head portion slidably engaged to the blade of the combination square. It was specifically designed to set the height of a tale saw, to set the position of a rip fence, to set the drill depth on a drill press, etc. It does not address the rotational problems discussed above.
U.S. Pat. No. 3,533,165, issued in the name of Larsen, discloses a vernier attachment for a combination square. However, this device is only designed to assist in the measurement of distances parallel to the blade of the combination square. As such, it does not address the rotational problems of squaring a surface area discussed above.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention.
Consequently, a need has been felt for providing an apparatus which overcomes the problems cited above.